It is known to granulate powdery materials such as, e.g. precipitated silica by simultaneously deaerating, compressing and shaping the material. The apparatus used for this purpose consists of a gas porous filter roll arranged in a housing and connected to a suction device and a second roll in the housing arranged parallel to it and running counter to it. The second roll, having a selected profile is mounted with the first roll with a means for exerting a pressure holding the rolls together with the pressure maintained constant through a controllable pressure producer such as disclosed in German Pat. No. 1807714, and related Reinhardt U.S. Pat. No. 3,738,785. The entire disclosure of Reinhardt is hereby incorporated by reference and relied upon.
The known process has the disadvantage that any increase in output is limited. Another disadvantage is that the fluctuating bulk densities of the powders being granulated change the granulating output because the introduction of powder is only carried out via self-suction.
The problem of the present invention is to find how to increase the capacity of the known apparatus beyond that presently obtainable.